// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_EVENTS_EVENT_TARGET_ITERATOR_H_
#define UI_EVENTS_EVENT_TARGET_ITERATOR_H_

#include <vector>

namespace ui {

class EventTarget;

// An interface that allows iterating over a set of EventTargets.
class EventTargetIterator {
public:
    virtual ~EventTargetIterator() { }
    virtual EventTarget* GetNextTarget() = 0;
};

// Provides an EventTargetIterator implementation for iterating over a list of
// EventTargets. The list is iterated in the reverse order, since typically the
// EventTargets are maintained in increasing z-order in the lists.
template <typename T>
class EventTargetIteratorImpl : public EventTargetIterator {
public:
    explicit EventTargetIteratorImpl(const std::vector<T*>& children)
        : begin_(children.rbegin())
        , end_(children.rend())
    {
    }
    ~EventTargetIteratorImpl() override { }

    EventTarget* GetNextTarget() override
    {
        if (begin_ == end_)
            return NULL;
        EventTarget* target = *(begin_);
        ++begin_;
        return target;
    }

private:
    typename std::vector<T*>::const_reverse_iterator begin_;
    typename std::vector<T*>::const_reverse_iterator end_;
};

} // namespace ui

#endif // UI_EVENTS_EVENT_TARGET_ITERATOR_H_
